Hot-fill plastic bottles are designed to receive a liquid product at about 185 degrees F. Often, vacuum panels are disposed around the circumference of the body of the bottle. The vacuum panels are pulled inward in response to vacuum inside the bottle caused by cooling and contraction of the contents after hot-filling and sealing. The deflection of the panels enables the remainder of the bottle to have its desired shape.
In many hot-fill bottles, a waist is located above the panels. An example of a bottle having a conventional waist 3 is shown in FIG. 1. The conventional waist is typically formed by a relatively deep, concave (when viewed from outside the bottle), unbroken rib that extends around the circumference of the bottle between the body portion 4 (having the panels) and the dome 5. The conventional waist typically has a uniform cross section about the circumference.
A main purpose of the waist is to increase provide support just above the vacuum panels to help keep the bottle dome (above the waist) and the bottle body (below the waist) circular after hot filling. Without waist support, the bottle may become oval or kinked by internal vacuum because, for example, (i) the panels might not all deflect by the same magnitude or at the same time, (ii) the sidewall thickness may not be uniform around the circumference of the bottle, (iii) orientation or heat treating or cooling of the bottle may not be uniform, or a combination of these and other reasons.
The top load rating of the bottle, and of the waist, is important for stacking and filling. Conventional waist configurations have the drawback of poor top load performance. In this regard, when a downward load is applied to the top of the container, the force is transmitted through the dome to the upper part of the waist, where a large bending moment is created. Conceptually, the innermost part of the waist forms a hinge about which the upper and lower walls may pivot. Conventional waists, which often are not covered by a label because of their positions at the base of the dome, are also generally considered unappealing to consumers.
U.S. Pat. No. 6,932,230 (Pedmo) discloses a hot fill container having a discontinuous rib in its body below the waist and above its vacuum panels. U.S. Pat. No. 6,036,037 (Scheffer) discloses a hot fill container having a row of rib segments in its body above and below its vacuum panels. Both the Pedmo and Scheffer references disclose a conventional waist.
There is a general need for improved waist configurations in containers.